Portable keyboard



FIG. 1 is a top, front and side perspective view of a portable keyboard;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a rear elevation view thereof;

FIG. 6 is a left elevation view thereof; and,

FIG. 7 is a right elevation view thereof.

The portions of the drawings shown in broken lines, including depictions of the keys illustrate environment only and form no part of the claimed design. 

The ornamental design for a portable keyboard, as shown and described. 